In recent years, as disk-shaped information recording mediums capable of high-density information recording, so-called DVD (digital versatile disc) devices are generalized. In addition, data-writable DVD devices, such as DVD-R (DVD-Recordable) devices capable of only one time recording and DVD-RW (DVD-Rewritable) devices capable of multi-time rewriting are used in practical application.
Conventionally, in the case of optical disks, such as writable optical disks, it is known that in the event of recording contents data, the contents, a title thereof, and the like of recorded contents data are printed or written by an inkjet printer or handwriting on a surface (“label surface”, hereafter) of an optical disk different from a surface (“data recording surface”, hereafter) bearing the recorded contents data for identification of the disk from other optical disks or for indicating the recorded contents.
In addition, recently, in the case of such writable optical disks, it is known that the contents of contents data, a title thereof, and the like are recorded as visual information onto a free area of the data recording surface by using a laser beam or laser light.
In the case of DVD devices of the type recording the contents of contents data on the data recording surface, an irradiation portion and non-irradiation portion of laser light are formed on the data recording surface. The laser light irradiation portion and non-irradiation portion cause variations in optical characteristics to thereby record the visual information (see Patent Document 1, for example).
Patent Document 1: Japanese Patent Application Laid-Open No. 2001-283470